From: Indu Bhagat <indu.bhagat@oracle.com>
To: Jens Remus <jremus@linux.ibm.com>, binutils@sourceware.org
Cc: Andreas Krebbel <krebbel@linux.ibm.com>
Subject: Re: [PATCH v3 10/15] gas: Skip SFrame FDE if FP without RA on stack
Date: Thu, 18 Apr 2024 13:35:06 -0700 [thread overview]
Message-ID: <d21b5350-b2fb-40fa-8357-c24893850be9@oracle.com> (raw)
In-Reply-To: <20240412144718.4191286-11-jremus@linux.ibm.com>
On 4/12/24 07:47, Jens Remus wrote:
> The SFrame format cannot represent the frame pointer (FP) being saved
> on the stack without the return address (RA) also being saved on the
> stack, if RA tracking is used.
>
> A SFrame FDE is followed by 1-3 offsets with the following information:
>
> Without RA tracking:
> 1. Offset from base pointer (SP or FP) to locate the CFA
> 2. Optional: Offset to CFA to restore the frame pointer (FP)
>
> With RA tracking:
> 1. Offset from base pointer (SP or FP) to locate the CFA
> 2. Optional: Offset to CFA to restore the return address (RA)
> 3. Optional: Offset to CFA to restore the frame pointer (FP)
>
> When RA tracking is used and a FDE is followed by two offsets the
> SFrame format does not provide any information to distinguish whether
> the second offset is the RA or FP offset. SFrame assumes the offset to
> be the RA offset, which may be wrong.
>
> Therefore skip generation of SFrame FDE information and print the
> following warning, if RA tracking is used and the FP is saved on the
> stack without the RA being saved as well:
>
> skipping SFrame FDE due to FP without RA on stack
>
OK.
One comment below, otherwise LGTM.
Thanks
> gas/
> * gen-sframe.c (sframe_do_fde): Skip SFrame FDE if FP without RA
> on stack, as the SFrame format cannot represent this case.
>
> Signed-off-by: Jens Remus <jremus@linux.ibm.com>
> ---
>
> Notes (jremus):
> Changes v2 -> v3:
> - New patch.
>
> Without this patch the assembler would generate incorrect SFrame
> information without warning for the s390-specific SFrame error test
> case 5, that gets introduced by patch "s390: Initial support to
> generate .sframe from CFI directives in assembler". The FRE would
> be followed by two offsets for the CFA and FP. SFrame would
> erroneously interpret them as CFA and RA offsets, as it cannot
> represent FP without RA on stack.
>
> gas/gen-sframe.c | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/gas/gen-sframe.c b/gas/gen-sframe.c
> index a3b6f75cfe85..87be3eb05ad2 100644
> --- a/gas/gen-sframe.c
> +++ b/gas/gen-sframe.c
> @@ -1439,6 +1439,25 @@ sframe_do_fde (struct sframe_xlate_ctx *xlate_ctx,
> = get_dw_fde_end_addrS (xlate_ctx->dw_fde);
> }
>
> +#ifdef SFRAME_FRE_RA_TRACKING
> + if (sframe_ra_tracking_p ())
> + {
> + struct sframe_row_entry *fre;
> +
> + /* Iterate over the scratchpad FREs and validate them. */
> + for (fre = xlate_ctx->first_fre; fre; fre = fre->next)
> + {
> + /* SFrame format cannot represent FP on stack without RA on stack. */
> + if (fre->ra_loc != SFRAME_FRE_ELEM_LOC_STACK
> + && fre->bp_loc == SFRAME_FRE_ELEM_LOC_STACK)
> + {
> + as_warn (_("skipping SFrame FDE due to FP without RA on stack"));
> + return SFRAME_XLATE_ERR_NOTREPRESENTED;
> + }
> + }
> + }
> +#endif /* SFRAME_FRE_RA_TRACKING */
> +
There is a comment "/* No errors encountered. */" at line 1452 (few
lines above the proposed diff after applying). I suggest we also remove
/ move that comment too.
> return SFRAME_XLATE_OK;
> }
>
next prev parent reply other threads:[~2024-04-18 20:35 UTC|newest]
Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-12 14:47 [PATCH v3 00/15] sframe: Enhancements to SFrame info generation Jens Remus
2024-04-12 14:47 ` [PATCH v3 01/15] x86: Remove unused SFrame CFI RA register variable Jens Remus
2024-04-12 14:47 ` [PATCH v3 02/15] gas: Enhance arch-specific SFrame configuration descriptions Jens Remus
2024-04-18 7:39 ` Indu Bhagat
2024-05-03 12:30 ` Jens Remus
2024-04-12 14:47 ` [PATCH v3 03/15] readelf/objdump: Dump SFrame CFA fixed FP and RA offsets Jens Remus
2024-04-18 7:39 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 04/15] readelf/objdump: Display SFrame fixed RA offset as 'f' in dump Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 05/15] gas: Print DWARF call frame insn name in SFrame warning message Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 06/15] gas: Skip SFrame FDE if CFI specifies non-FP/SP base register Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 07/15] gas: Warn if SFrame FDE is skipped due to non-default return column Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 08/15] gas: Refactor SFrame CFI opcode DW_CFA_register processing Jens Remus
2024-04-18 7:40 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 09/15] gas: User readable warnings if SFrame FDE is not generated Jens Remus
2024-04-18 20:33 ` Indu Bhagat
2024-05-03 12:30 ` Jens Remus
2024-05-03 23:41 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 10/15] gas: Skip SFrame FDE if FP without RA on stack Jens Remus
2024-04-16 13:14 ` Jens Remus
2024-04-17 23:56 ` Indu Bhagat
2024-04-18 10:27 ` Jens Remus
2024-04-18 20:35 ` Indu Bhagat [this message]
2024-04-12 14:47 ` [PATCH v3 11/15] gas: Skip SFrame FDE if .cfi_window_save Jens Remus
2024-04-18 20:36 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 12/15] gas: Don't skip SFrame FDE if .cfi_register specifies RA w/o tracking Jens Remus
2024-04-18 20:36 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 13/15] gas: Don't skip SFrame FDE if .cfi_register specifies SP register Jens Remus
2024-04-18 20:37 ` Indu Bhagat
2024-04-19 13:13 ` Jens Remus
2024-04-23 8:15 ` Indu Bhagat
2024-04-25 22:22 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 14/15] gas: Test predicate whether SFrame RA tracking is used Jens Remus
2024-04-18 20:37 ` Indu Bhagat
2024-04-12 14:47 ` [PATCH v3 15/15] gas: Validate SFrame RA tracking and fixed RA offset Jens Remus
2024-04-18 20:38 ` Indu Bhagat
2024-05-03 16:40 ` Jens Remus
2024-05-04 0:22 ` Indu Bhagat
2024-05-06 11:41 ` Jens Remus
2024-05-06 14:39 ` Jens Remus
2024-05-16 20:45 ` Indu Bhagat
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=d21b5350-b2fb-40fa-8357-c24893850be9@oracle.com \
--to=indu.bhagat@oracle.com \
--cc=binutils@sourceware.org \
--cc=jremus@linux.ibm.com \
--cc=krebbel@linux.ibm.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).